Electric heating pad and fabric



Feb. 19, 1929. 1,703,005

. F. w. HEWITT ELECTRIC HEATING PAD AND FABRIC Filed Jan- 5, 1928 2sheets-sheet 1 Feb. 19, 1929.

F. W. HEWITT ELECTRIC HEATING PAD AND FABRIC Filed Jan. 5 I928 2Sheets-Sheet 2 5&6: 7

M w W Patented Feb. 19, .1929.

UNITED STATES rnanx w. rmwrr'r, or ARLINGTON,- irassacmrsn'r'rs.

ELECTRIC HEATING PAD AND FABRIC.

Application filed January 5, 1928. Serial No. 244,744.

This invention relates to flexible electric heating pads and the likewherein a resistance wire is disposed on and is supported by a flexiblefabric in such a manner as to provide a flexible construction and todistribute heat approximately uniformly over the surfaces of the pad.

Heating pads of the type above set forth have usually contained arelatively high resistance wire as the heating element, which wire maybe in the form of a spiral or coil; and the wire is usually contained ina heat insulating sheath and has only a relatively .few folds.

It is an object of this invention to provide a flexible electric heatingpad consisting of a flexible woven fabric having warp strands of textilefibres and having the woof cons1sting of a continuous strand of fibrousmaterial wound with a, spirally-formed contmu ous electric conductor oflow resistance, which conductor is without a heat-insulating sheath andis exposed for free heat radiation 1 and convection from its surface. Afurther object of the invention is the pro vision of an electric heatingpad having its opposite covers, or faces, formed of mate rials havingdifferent heat-conducting properties, whereby different degrees of heatmay be obtained merely by placing one or the other side of the pad incontact with the body to receive heat.

A further object is generally to im rove the construction of electricheating pa s.

A yet further object is an improved method .of manufacturing electricheating pads.

Fig. 1 is a plan detail illustrating the manner of making the heatingfabric embodying the invention.

Fig. 2 is an enlarged side elevation of Fig. 1.

Fig. 3 is afragmentary plan view of a woven heating fabric drawnapproximately to full scale.

Fig. 4 is a detail of the heating element and illustrating moreparticularly the construction thereof.

Fig. 5 is an enlarged plan detail of'a heating fabric adapted for usewith a similar 50 heating fabric having a. heating elementof a differentresistance and wherein the heating element bears an identifyingcharacteristic.

Fig. 6 is a plan view of a heating pad conss structed in a rdance withthe invention and with a portion of the external cover removed to exposea heating fabric.

Fig. 7 is a section along line 77 of Fig. 6 and illustrating moreparticularly the internal construction of the heating ad.

Fig. 8 is, a section similar to Flg. 7 but illustrating a modifiedconstruction wherein the superimposed heating fabrics are formed from acontinuous section of fabric.

As here shown the Woven heating fabric embodying the invention comprisesthe textile strands 10 which form the warp of the fabric. Said warpstrands may consist of cotton or other fibres; and the strands may berelatively widely spaced apart, say about one-eighth of an inch, or asillustrated in Fig. 2. The warp at the edges of the fabric may have adouble strand, as at 10*, whereb to provide increased strength at theside e es. Thewoof of the fabric comprises a heating element 11, and thewarp and the woof may be Woven in any suitable manner, as to form asimple basket-weave, as shown. The heating element, or woof, iscontinuous and is woven with the warp in such a manner that the warpstrands hold the adjacent folds or strands of the heating element inspaced relation; and the spacing between the folds of the heatingelement may be about equal to the spacing between the warp strands.

The heating element may include a flexible core 13 of textile fibres, ascotton for instance. A continuous electrically conducting wire 14 iswound in a spiral mannerover said core, to secure flexibility, and theconvolutions of said wire are spaced from each other, whereby to providefree access of air to the surface of the convolutions. Preferably theheating element, comprising the wire and core, has a diameter aboutequal to that of the warp strands, whereby a uniform woven fabric mayresult. Said electric conductor is preferably of fine enamel-insulatedcopper Wire, whereby to provide for a large extent of wire and,therefore, large heatdissipating surface although any other wire havingsimilar characteristics may be used. I

In the process of manufacture, the fabric is woven in long len hssuflicient to form a large number of smal er heatin fabrics. The heatingelement comprising t .e woof, is interwoven with tlie'warp strands untila sufficient length of heating element is woven to produce a heatingfabric having the desired characteristics, as power consumption, etc.,

whereupon the heating element is passed along the outside of the warpstrands for a suitable distance and then again interwoven with the warpstrands, and this process is re peated as desired. The long fabric isthus formed with woven sections a connected and separated by unwovensections 5 occupied aplurality of heating fabrics having the sam powerconsumption. Preferably, howei er, and particularly for heating padshaving two heating elements or fabrics having different rates of powerconsumption, the procedure is different; and the preferred method isillustrated in Fig. 2. .A long length of fabric woven as above set forthhas superimposed upon it a suitable fabric supporting sheet 16. A secondlong length of heating fabric issuperimposed upon the supporting fabricin such a manner that the woven portion a and unwoven portions 6 of thetwo heating fabrics are in vertical register. Spaced lines of stitching17 are then passed through all of the sheets, in the unwoven portions ofthe heating fabrics; and the stitching serves to unite allthesuperimposed fabrics together and also to bind the warp strands of theheating fabrics in place. 7 The united and superimposed fabrics may beout between the lines of stitching, as at w-ca, and each section, whenthe heating elementsare properly connected electrically, is in readinessto be inserted in the covers of a heating pad. If the heating pad isdesigned, however, to have two heating fabrics of the same powerconsumption, I may cut the long fabric into short sections eachcontaining two woven sections separated by unwoven warp strands,

and fold the short section to superpose the woven sections asillustrated in Fig. 7 and the warp strands may be continuous throughoutboth upper and lower heating fabrics. If

I the heating pad is designed to have two heating fabrics havingdifferent rates of power consumption, I'prefer to weave two sets offabrics, similar to that illustrated in Fig. 1, but with differentheating elements, and I may form one heating element with an identif ingcharacteristic, as by weavin a colored t need 12 thereon Fig. 5, wherereadily to identify thegdiiferent heating fa rics.

* The heating elements of the superposed heating fabricsmay' beconnectedto an electric circuit in any well known manner, and

by suitable means as the switch 20, whereby to obtainapluralit pf heats.One or more thermostat! 18, o more or less usual construction, may bedisposed between-er upon said superposed fabricate be heated by. bothfabrics, and included in 'the circuit through the heating elements in amore or less common manner to protect said heating elements against anundue elevation of temperature- The heating fabrics are adapted tobeenclosed within an enclosing casing formed, preferably, of two sheets ofmaterial, or covers, having dissimilar heat-conducting characteristicsand united together by suitable means as the lines ofstitching 21. Onesheet or cover, as the sheet 23, may have the property of being arelatively good heat conductor and the other sheet, as the sheet 24;,may have the property of conducting heat at a slower rate than that ofsaid first sheet. With this arrangement, when the cover 23 is in contactwith the bodyto be heated, the effect of a high heat may be obtained,and when the cover 24 is in contact with the body, the effect of a lowerheat maybe obtained, and without altering the electric connections ofthe heating elements.

The connection of heating elements with the power circuit, under controlof the switch 20, is adapted to be such that three dilferent heats maybe obtained. Since thecovers 23 and 24 provide'one additional heat witheach circuit ar angement of the heating elements, as ordinarily but oneside of the heating pad is used at one time the above describedconstruction of the covers provides a pad having a total of six heats.

The cover sheets 23., and 24 are preferably made of relatively soft andflexible materials.

The cover sheet 23,fo1i instance, may be made of suitably pre aredcotton which permits heat to be con ucted through it at a relativelyrapid rate. The cover sheet 24 may be made of eiderdown, for instance,through which heat may be conducted at a slower rate.

It is to be noted that the weave of the heating fabrics and the relationof the fabrics and the cover-sheets is such that air ockets 26 areformed, in which air pockets t e heating elements are disposed; and heatmay be radiated from the heating conductor directly to the cover-sheetsof the pad; and the air has free access to the surface of the heatingelements and may circulate freely over the heated surface thereof andgive up its heat to the cover-sheets, whereby to heat said cover-sheetsuniformlyover practically their entire extent.

I claim:

1. An electric heating pad including a fiexi ble loosely woven heatingfabric having a warp com. osed of strands of spaced textile fibres, anda homogeneous woof of continuous fibrous materialwo'und with an exposedI fine co per wire with the convolutions thereof space apart. 2.Anelectr'ic heating pad including, a flexible loosely woven heatingfabric having a warp composed of strands of spaced textile fibres, and ahomo eneous-woof of continuous fibrous materia wound with an exposedfine copper wire with the convolutions thereof spaced apart, and afabric enclosure for said heating fabric.

3. An electric heating pad having two layers of loosely Woven heatingfabric made as described in claim 1, stitched to an interveningsupporting fabric.

4. An electric heating pad having two layers of loosely woven heatingfabric made as described in claim 1, stitched to an interveningsupporting fabric, and a fabric enclosure for said fabrics.

5. An electric heating pad having opposed heat-conducting faces, eachcomposed of materials having different heat-conducting properties, andan electric heating element disposed between said opposedheat-conducting faces. 7

6. An electric heating pad having an electric heating element includingmeans to provide a plurality of heats therefrom, and an enclosing casingfor said'heating elementhaving opposed heat-conducting covers composedof materials having different heat-conducting properties.

7. 'An electric heating pad having a flexible loosely woven heatingfabric made as described in claim 1 and enclosed in a flexible casinghaving two opposed cover-sheets coning supporting fabric and allenclosed in a flexible casing having two opposed coversheets constructedof materials having different heat-conducting properties.

9. Asa new article of manufacture, a flexible woven heating fabriccomprising a plurality of spaced woven sections consisting of insulatingwarp strands and electrically conducting woof strands, the wovensections being connected b unwoven sections having warp strands n y andbeing free from said I attached fabrics between the lines of attachment.

11. The method of manufacturing electric heating pads which consists informing two separate lengths of flexibleheating .fabric, each lengthhaving s accd woven sections including a heat-ing e ement, andintervening unwoven sections, superposing said lengths of fabric withtheir woven and unwoven sections in, vertical register and with a lengthof a flexible textile supporting fabric interposed between the heatingfabrics, attaching all fabrics together along two spaced transverselines located theunwoven sections of the heating fabrics, and cuttingsaid attached fabrics betwe'en'the lines of attach- 'ment.

In testimony whereof, I have signed my name to this specification.

FRANK W. HEWITT.

